• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.176-180
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• 2007

In the case that an overcurrent flows through in electrical wire due to short-circuit or overload, the wire can be fused, thereby causing an electrical fire. In the present article the characteristics of the fusing current of an electrical wire have been studied to discriminate between short-circuit and overload. In the experiment the fusing time was measured as the currents determined by Preece's equation were supplied to bare wires of various diameter. As the results of experiment, the measured fusing currents well satisfied the Onderdonk's equation. By comparing the measured results and the short current the IEC recommends, it is shown that the variable to determine the short current for a bare copper wire, k is appoximately 300. The fusing current of an electrical wire which becomes a short circuit within 5sec can be expressed as a function of diameter based on the value of k. Consequently, the equation for the fusing current provides a criterion to discriminate between short-circuit and overload.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3455-3459
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• 2014

This paper reports the design and experiments for a high drive force of projectile in a coil gun system. Currently, the coil gun has been studied to apply an electromagnetic launcher. A coil gun launches a projectile by the attractive magnetic force of the electromagnetic coil. The drive force of projectile is proportional to the magnetic force generated by the electromagnetic coil. The current affects the life of the coil and the current limit exists. Therefore, the coil gun design, which does not exceed the current limit and the magnetic forces are at the maximum, is required. For this purpose, this study calculated the magnetic flux density and forces of the coil gun system and determined the current limit of the coil using the Onderdonk's equation. Based on the design result, a prototype was manufactured and an experiment was conducted to measure the muzzle velocity of the projectile. The fired projectile was analyzed using a CCD camera, and the muzzle velocity was 21m/s. In addition, a comparison of the experimental value and analysis value using commercial electromagnetic analysis software MAXWELL revealed an error of approximately 9.5%.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.408-412
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• 2014

An electromagnetic launching system presents a viable projectile propulsion alternative with low cost and minimal environmental drawbacks. A coil gun system propels a projectile using an electromagnetic force and the system is mainly employed in military weapon systems and space launch systems. In this paper, we perform optimization design to improve the muzzle velocity by analyzing the sensitivity. The muzzle velocity, which is the most important design function variable, is affected by design variables including the number of axial turns in the electromagnetic coil, number of radial turns in the electromagnetic coil, initial distance between the projectile and the coil, inner radius of the electromagnetic coil, and length of the projectile. An orthogonal arrays matrix is configured, and a finite element analysis is performed utilizing the commercial electromagnetic analysis software MAXWELL. The muzzle velocity of the optimal design is 62.4% greater than that of the initial design.